Process of and apparatus for producing acetylene and ethylene



Jan. 3, 1961 c. J. coal-:RLY 2,967,205

PROCESS OF AND APPARATUS FOR PRODUCING ACETYLENE ANDk ETHYLENE Filed sept. 24, 195e v s sheets-sheet 1 43a i .S7 44a F/cg. l. 43

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United Safes Pare-nf 0 PROCESS OF AND APPARATUS FOR PRODUCING ACETYLENE AND ETHYLENE Clarence J. Coberly, San Marino, Calif., assigner to Wulff Process Company, Huntington Park, Calif., a corporation of California Filed Sept. 24, 1956, Ser. No. 611,541

13 Claims. (Cl. 260-679) The invention relates to the production of an off-gas or cracked gas containing a desired hydrocarbon such as, for example, acetylene, or ethylene, and other olens, from an in-gas containing a suitable hydrocarbon, such as, for example, propane, by the pyrolysis of the in-gas in a suitable regenerative furnace.

The nature and substance of the invention may be briefly summarized as comprising a new and useful method of, and apparatus for, operating a novel and useful furnace which may be used to pyrolyze hydrocarbons.

A primary object of the invention is to provide such a furnace having heating means adapted to permit the size of the furnace, and consequently its capacity, lto be varied through a wide range without substantial variation in yield of the desired hydrocarbon.

A further object is to provide such a furnace having 2,967,205 Patented Jan. 3, 1961i` ICC Fig. 13 is a diagram illustrating the cooling system of the invention.

Fig. 14 is a view similar to Fig. l1 of an alternative form of fuel nozzle.

A furnace 11 adapted for use in my invention is diagrammatically illustrated in Fig. 1. It consists of -a steel shell 12 having a heat insulating lining 13. Carried quenching means adapted to eiciently and rapidly quench the cracked gases formed by pyrolysis in the furnace to temperatures at which the desired hydrocarbon is stable. Another related object is to maintain the temperature of the quenching means above the dew point of tarlike materials in the cracked gas, to prevent the deposit of such tarlike materials.

Still another object of the invention is to provide such a furnace with fuel injection means adapted to efficiently supply fuel thereto to promote uniform combustion therein. so that the fuel injection means is maintained at a temperature below the temperature at which the fuel would be cracked to form undesirable tarlike materials.

Other objects, features, and advantages will appear from the following specification and the drawings, which are for the purpose of illustration only, and in which:

Fig. l is a diagram,- partly in vertical section, showing the furnace of my invention and Ithe piping and auxiliary apparatus adapted to produce a desired hydrocarbon from a suitable hydrocarbon. v

Figs. 2, 3, 4, and 5, are diagrams illustrating the four steps of a cyclic process used to practice my invention.

Fig. 6 is a transverse vertical section through the furnace on a plane indicated by `the line 6 6 in Fig. 8.

Fig. 7 is a transverse vertical section through the furnace on a plane indicated by the line 7-7 in Fig. 8.

Fig. 8 is a longitudinal vertical section of a portion of the furnace on a plane indicated by a line 8-8 in Fig. 6.

Fig. 9 is a longitudinal section through a portion of a quencher and quencher tube of the invention on a plane indicated by a line 9-9 in Fig. 12.

Fig. l0 is a cross section on a plane indicated by a line 10-10 in Fig. 9. l

Fig. 11 is a longitudinal section through a portion of a quencher and fuel nozzle on a plane indicated by a line 11--11 in Fig. 12.

Fig. l2 is a cross section through a portion of a quencher and fuel nozzle on a plane indicated by a line lg-lzinFig. 11.

A related object is to operate such a furnace f inside the lining 13 are three spaced regenerative masses 15, 16, and 17 `providing four spaces, a left-hand end space 21, a left central space 22, a right central space 23, and a right-hand end space 24, as viewed in Fig. 1. Each of the regenerative masses has a plurality of longitudinal channels 25 which extend longitudinally through the mass, the channels 25 connecting the spaces 21 to 24 in a chain of openings through which gas may pass from the left end space 21 to the right end space 24, or vice versa. A pipe 26 delivers gas to, or takes it from, the left-hand end space 21 and a pipe 27 delivers gas to, or takes it from, the right-hand end space 24.

Air under pressure may be delivered to the pipe 26 through a valve 31 and to the pipe 27 through a valve 32. Waste products of combustion may be delivered to a stack from the pipe 26 through a valve 33 and from the pipe 27 through a valve 34. Off-gas or cracked gas may be taken from the pipe 26 through a valve 35 and from the pipe 27 through a valve 36. In-gas may be delivered to the pipe 26 through a valve 37 and to the pipe 27 through a valve 38. In-gas may be a mixture formed in a mixer 40 of a diluent such as steam, delivered through a valve 41, and a suitable hydrocarbon delivered through a valve 42. Fuel gas may be de.4 livered to the space 22 through a valve 43'and to the space 23 .through a valve 44. Also, steam may be delivered'to the space 22 through a valve 43a and to the space 23 through a valve 44a.

Various processes may be carried on by the mech- -anism shown in Fig. 1 and above described. For example, an off-gas containing acetylene or ethylene, or both, may be produced from an in-gas containing propane, in a four-step process which will now be descrbed. Before this process can be started, the masses 15, 16, and 17 must be preheated. Such preheating can .be conveniently performed in two steps. Each of the spaces 22 and 23 has a torch opening 46 which is normally closed by a plug 47. All of the valves 31 to 38, 41 to 44, 43a and 44a being closed, the valve 34 is opened, thus connecting the space 24 with the stack. The lefthand plug 47 is then removed from its opening communicating with the space 22 and hot gas or flame from a torch is fed into the space 22 through the opening 46 and the hot gas therefrom passes through the channels 25 in masses 16 and 17 and this hot gas tends to heat masses 16 and 17 before passing through the pipe 27 and valve 34 to the stack. The torch is then withdrawn from the hole 46 in the space 22 and the plug 47 is replaced and the valve 34 is closed. The valve 33 is then opened, the right-hand plug 47 is removed from its opening 46 into the space 23 and hot gas or flame is passed from a torch into the space 23 and the hot gas therefrom passes through the channels 25 in the masses 16 and 15 and through the pipe 26 and the valve 33 t0 the stack. This accomplishes the preheating step. i

As as alternative method of performing the initial preheating step is, with all of the valves 31 to 38, 41 to 44, 43a and 44a being closed, the valve 33 is opened to the stack, the fuel valve 44 is partially opened to permit fuel to ilow into the right central space 23, the air valve 32 is opened to permit air to pass to the right end space 24 and through the channels 25 in the right-hand mass 17 into the space 23 where it mixes with fuel, the mixture being ignited through the right-hand port 46 which is then closed. The hot products of such combustion then pass from the space 23 through the mass 16, the space 22, and the mass 15 to the stack through the pipe 26 and the valve 33, which heats the masses 16 and 15. When the masses 16 and 15 have attained a desiiedtemperature, the valves 32, 33, and 44 are closed and valves 31, 34 and 43 are opened to a required extent to p ermit air to pass through the valve 31, the left end-space21, and the mass 15 into the left central vspace 22 where it mixes with fuel admitted thereto through the valve 43. Such mixture in the space 22 is then ignited and the `hot products of such combustion then pass through the mass 16, the right central space 23, the mass 17, and the valve 34 to the stack. This is continued until the mass 17 fate tains a desired starting temperature, which completes this alternative form of preheating step.

it will be noted that in the preheating step the mass 16 hasbeen heated by both aleft-to-right and a right-to-left flow of hot gas. The central mass 16 is, therefore, much hotter than either of the masses 15 or 17. Also, both of the masses 15 and 17 will be much hotter at their inner ends adjacent to the spaces 22 and 23 than at their outer ends adjacent to the end spaces 21 and 24.

Such preheating step should be performed prior to starting cyclic production of the desired hydrocarbon, such as acetylene, but the cycle now to be described maintains the masses in proper heat condition as long as the cycle persists, subject, however, to brief interruptions of the cyclic process at long intervals of time when it-is desired to correct any undesired distribution of heat in the masses.

The four steps of the cyclic process whichv is chosen to illustrate one use of the invention claimed hereinA are illustrated -by Figs', 2, 3, 4, and 5, and will now be described.

Preparatory to the cycl-icprocess next to be described the furnace has been preheated'as'previously described. For the manufacture ofacetylene the centralfmassl during the cyclic step may be at a Vtemperature somewhat higher than 2200 F. and the masses 15 and 17 are at a temperature somewhat lower than 2200" F. adjacent to the central spaces 22 and 23 and at'a much lower temperature at their outer ends adjacent to their respective end spaces 21 and 24. For the production of ethylene primarily, or a mixture of lethylene and acetylene, such temperatures 'may ,be somewhat lower to obtain optimum yields; Also, a'swill be understood, if in the r'prelieating step the Vhot products of combustion are last passed lfrom right-to-left, as seen in Fig. 1, the center ma-ssf16 andrthe left-hand mass 15 will be at a higher temperature than the right-hand mass 17 and in the initial make step the in-gas should be passed from left-to-right. However, if in the preheating step the hot products of combustion are last passed from left-to-right the center mass 16 andthe right-hand mass 17 will be at a higher temperature than the left-hand mass 15 and in this case in the initial make step the in-gas should be passed from right-to-left. It is immaterial which Way the cyclic operation is started,

During the LH make step as shown in Fig. 2 an ingas is formed by mixing a suitable hydrocarbon, such as propane, delivered to the mixer 40 through the valve 42, with a diluent, such as steam, admitted to the mixer 40 through the valve 41, the in-gas so produced being d elivered through the valve 37 and the pipe 26 tothe lefthand end space 21 of the furnace 11. VThe in-gas Hows from left-to-right through the furnace 11 and is pyrolyzed in the furnace 11 to form an off-gasncontainingY a desired hydrocarbon, theYotf-gas being delivered lto other. apparatus, not shown or described, through the valve 36 .from the pipe 27. Such pyrolysis in the LH make step occurs principally in the center mass 16 but some also occurs in the left-hand mass 15. During the make step heat is withdrawn from the hot regenerative masses in thefurnace to (a) provide heat to bring the in-gas up to a certainreactive temperature and (b) to provide the heat necessary to perform'the pyrolysis.

The RH heat step shown in Fig. 3 may follow the LH make step. In the RH heat step, air is delivered through the valve 31 and the pipe 26 to the left-hand end of the furnace and passes from left-to-right through the furnace, being itself heated by and in turn cooling the mass 15. Fuel gas is delivered through the valve 43 to the space 22 Where it is mixed with the hot air delivered to the space 22 from the channels 25 in the Ymass 15 ,andYbu-rned. The products.. of such combustion pass rightwardly through the furnace, passing to the stack through the mass 16, the central space 23, the right-hand mass 17, the right end space 24, the pipe 27, and the, valve 34. This is continued until the center mass 16 and at least the inner end of the right-hand massf17 are raised above a desired pyrolysis temperature. This isfollowed by the RH make step. Y

The RH make step is shown in Fig. 4. The in-gas produced in the mixer 40 is delivered through the valve 38 and pipe-27 to the right-hand end of the furnace and passesV from right-to-left through the furnace 11, pyrolysis taking place principally in the center `mass 16, and to a lesser degree in the right-hand mass 17. The off-gas leaves the furnace through thevalve 35.

The LH heat step is shownin Fig. 5 and may follow the RH make process shownl in Fig. 4. In the LH heat step air is delivered to the furnace y11 through the valve 32 and the pipe 27, and'is mixed with fuel gas in the space 23 delivered to the spacevr23 through the valve 44 andiburned. The productsrof lcombustion are delivered to the stack through pipe 26 and the valvef33.

Disposed iu the central spaces y22 and 23 are transverse members 50 and 51, respectively, which arevidentical, except oppositely disposed, so'onlfythe member 51 will be `described in detail. The member 51, asbest shown in Figs. 6i 8, andv9to 13, inclusive, includesaf'general-ly rectangular container member 52 which isf preferably vinset through the top of thefurnacel v1ilinto'the right central-space 23. The container'mernber 52v has front and rear walls 52a and 5211, respectively, and a bottom wall 52C, as shown in Fig. 8, and side walls 52d and 52e, as shown in Fig. 6, andan integral head member 53 which is suitably secured in gastight relationsihp to the top ofthe shell 12. The container member 52 thus forms a closed box which completely covers ytransverselythe cross-sectional area of the right central space 23. Depending from the yhead'mernber 53 are fourfuel-pipes 54, the lower endsrofwhizch are closed and lthe upper ends of which are in ovpenj communication'with a manifold 'space 56,' provided by a coverlbell*57.Witb'which the fuel supply is connected vthroughwthevalve i4-and its piping.

Also suspended from the head'membei- 53 are two outer baffle plates 60 andl, the lowerends of which stop short of the bottom wall 52e, and supported by and extending upwardly from the bottom wall is a central bafe plate 62, the upper. end of which. stops short of the head member 53. lConnected to oppositesides of the head member 53 are coolant pipesv 63avand 63b which, as shown diagrammatically in Fig. 13, are connected to a heat exchanger 64, there, being a suitable pump 65 in the line of the pipe 63a. The pump 65 is adapted to circulate a suitable liquid from .the `heat exchanger through the pipe 63a 'into the container member 52 and therethrougharound vthe baiiie plates 60, 62, and

`61, as indicated by the arrows inligplS, and Athroughv the pipe 631) back through the heat` exchanger. Air is preferablyblown through lthe tubes (not shown) of the heat exchanger 64 'by a blower 66 to the valves V3 1au`d 32, or either, to be used in lthe heating Asteps `of the. method described herein.

Each of the depending fuel pipes 54 is provided with a plurality of fuelv nozzle assemblies y,71 ,(best shown in Figs.` 11 and l2). Eachof the fuel nozzle assemblies 71 has a body 72 of generally tubular.formv which is welded at 73 and 73a into suitable horizontally aligned yholes in the fr'on't and Vrear walls 52a and B2b, respectively. For convenience of manufacture, the depending fuel pipes 54 are made in short lengths and the appropriate ends are welded into suitable vertically aligned holes in the bodies 72, as indicated at 74. The body 72 is provided with a horizontally disposed conical opening 74a into which is driven a nozzle plug 75 which has a horizontal bore 76 partially therethrough and a plurality of circumferentially spaced radial bores 77 communicating with the interior of the fuel pipe 54 in which its fuel nozzle assembly is located. The bores 76 of the nozzle plugs'75 in the transverse member 51 open into the right central space 23 and are directed towards the central mass 16, and the similar bores in the transverse member 50 open into the left central space 22 and are directed towards the central mass 16, as indicated in Fig. 1.

As best shown in Fig. 6, the nozzle assemblies 71 are preferably spaced uniformly throughout the central space in which they are located, to provide a uniform fuel distribution in such vspace to insure a substantially uniform heating of the central mass 16 during both the LH and RH heating steps described hereinbefore, which is an important feature of the invention. With variations of the cross-sectional area of the central mass 16 the number of depending fuel pipes 54 and the number of nozzle assemblies 71 in each may be varied to readily provide a uniform fuel distribution for any desired crosssectiona'l area. Thus, if such area is increased, the number of fuel pipes 54 or nozzle assemblies 71, or both, may be increased, or, conversely, for smaller areas such Inumber may be reduced. This method of fuel distribution is particularly desirable in regenerative furnaces having a large cross-sectional area, in which it is virtually impossible to provide a uniform fuel distributiony across the entire area if the fuel is injected into the furnace by jets or nozzles in the sides of the furnace by conventional means.

Also connecting the front and rear walls 52a and 52b of the container 51 are a plurality of short flue tubes 81 which are arranged in a substantially uniform pattern between the fuel tubes 54 and the nozzle assemblies 71. As best shown in Fig. 9, each of the flue tubes 81 is welded at its ends to the front and rear walls 52a and 52h, as at 82. The total cross-sectional open area of the flue tubes 81 is preferably approximately equal to the total cross-sectional area of the channels 25 in the masses 15, 16, and 17 so that the velocity of passage of gas therethrough is substantially uniform, and this is a further object of the invention.

As will be noted, the coolant Which is circulated through the container 51 passes around the flue tubes 81 and serves to cool gas passing therethrough as desired.

Thus, during the RH make step the center mass 16 is at the relatively high temperature required for pyrolysis and the in-gas passes from the right end space 24 through the channels 25 in the right-hand mass 17 and then through the ue tubes 81 in the transverse member 51 and thence through the central mass 16 where the major part of the pyrolysis occurs, and into the left central space 22 from which the cracked gas ows through the ue tubes 81 of the transverse member 50 and thence through the left-hand mass 15 and out of the furnace. If at this time coolant is circulated through the transverse member 50 the cracked gas passing through the flue tubes 81 thereof is quickly cooled by such coolant to a temperature at which the desired hydrocarbon therein, such as acetylene, is stable, which provides a much circulated through the transverse member 51 serves to cool the cracked gas passing therethrough.

The coolant circulated through the transverse members 50 and 51 is necessarily a liquid having a relatively high boiling temperature, such as Dow Therm, which can be operated at temperatures of 600 F. to 700 F. without boiling, or by a liquid metal such as mercury, sodium, or lead. Due to the high temperatures existing ,in the furnace' 11 to obtain pyrolysis such a high temperature liquid will normally be circulated at temperatures in excess of 500 F. Thus, although such liquid yis generally referred to herein as a coolant for the the transverse member 51 through which such relatively hot coolant is being circulated.

Having described the function and operation of the apparatus qualitatively, the quantitive information will now be given so that anyone skilled in the art will be able to practice the invention and obtain the improved results to be derived therefrom.

In the furnace of the type described in which the ceramic masses 15, 16, and 17 each has a cross-sectional area of 2.5 square feet the heat duty thereof during each heating step will be 50,000 B.t.u. per minute in producing acetylene, or about 20,000 B.t.u. per minute per square foot 'of cross-section. Since this invention is applicable to'furnaces having a wide variation in sizes, the proportions given hereinafter will be on the basis of such a furnace having ceramic masses of one square vfoot in cross-section.

The fuel supplied to the fuel nozzles 71 will normally be olf-gas formed by the furnace during the make steps and after the acetylene or other desired product has been removed therefrom. Such off-gas normally has a heat value of about 500 B.t.u. per cubic foot. In producing acetylene from propane the composition of the off-gas Will be approximately as follows:

4.09 58.51 CH., 21.84 C2H4L 6.27 CZHG .1 CH4 .1 03H, .21 Co2 1.57

The heat value of such an olf-gas will be about 475 B.t.u. per cubic foot. Therefore, it will be necessary to burn 42 s.c.f.m. (standard cubic feet per minute)` per square foot of cross-sectional area of the ceramic masses. To accomplish this, I prefer to arrange the fuel nozzles 71 on approximately 4%" centers, to provide 6.4 fuel nozzles per square foot of cross-section, and each fuel nozzle will be required to burn 6.6 s.c.f.m. of the off-gas. If natural gas is used for fuel, it will have a heat value of about 1000B.t.u. per cubic foot, and therefore only 20 s.c.f.m. will be required, or about 3.1 s.c.f.m. per nozzle. As shown in Fig. 12, four orifices 77 are provided for each fuel nozzle 71, and suflicient pressure should be maintained in the fuel pipes 54 to provide an in-gas How through the orifices at the critical velocity of the in-gas, which is about 2500 feet per second. Therefore, for the use of such an off-gas as fuel each orifice 77 should have a diameter of about 0.06 inch. If natural gas is used as fuel, the diameter of each orifice should be about 0.05 inch.

The diameter of the bores 76 is not critical, but l have found that good results are obtained if the fuel velocity in ing during the make steps.

suchfbores is 'aboutthesame'as the artvelocity through the flue tubes 81. Since there are four .ue tubes `81 for each fuel nozzle 71 and the ratioofair to .off-gas for complete combustion is about 4.5 :1, the cross-sectional area of athe bore.76.should be .approximately 0.9 times the internal crossesectional. area vofthe ue tube 81. This ratiois reduced, however, lby theyfact that the temperature .of the Jair passing vthrough 'the tine :tubes8'11is approximately 1000 .C., while the v.fuel ;gas, passing through the bores'76.is.approximately=at theitemperature of the quenchertSi),` which is approximately 350 C. Allowing for this temperature ldifference, .the area ratio vof the bore 76 to .the flue tube 8'1will'-be approximately 0.43:1.

A further functionof the uertubes'fSl is .to impress a pressure drop on. the .gases flowing therethrough to equalize the ow through the :centralspaces 22 and 23 and to kact as distributors for the gases .to insure this result. AUnder the normalfoperating conditions required for optimum yields of acetylene, I have found that the internal diameter of the flue tubes 81 should be not less than one inch, which would give a pressure drop of about 0.175" of mercuryfstatic pressure, and'could be asrmuch as 11/4 inches, which would reduce the pressure drop to 0.109" ofmercury.

In designing the quenchers 50 and 51, the matter of heat transfer from thehot cracked gasto the quencher should be considered. `For optimumfquenching, the temperature of the gas -zshould be reduced .at the rate of about 20,000" C. persecondforhigher, andit is desirable to reduce the temperature. of :thegas at least 200 C. during passage through thegquencher. The quantityof .cracked gas to ibe'cooledlis 120 s-.c;f.r n. per square foot of crosssection of fthe linterior .of therfurnace, and, in addition, 155 s-.c.f.m;.ofsteammustbe quenched,fwhich will require a total of 2550 B.t.u. perrninute. -The flue tubes 81 are spaced onv 2%; inchgcenters;providing' 28.5 tine tubes per square footof'quenehervarea. Using flue tubes of one inch Vdiameter and-two inches long, the quenching area provided thereby is v1.24l squarefeet of face area on the quencher. However, most of the heat transfer is by radiation, 'and hence the-faces'of the quenchers 50 and 51 will transfer-heat aswell as, thesurfaces of the flue tubes 81. The total available quenching area, therefore, is 3.24 square `feet per 'Square foot .of

gross area of the quencher. "Since the heat"'transfer is ,proportional "to T1'4#T4, the transfer 4at 2500 1R. .and 1l40 R., which 'are absolute 'temperatures of the gas :and quencher respectively, will be 3500"B.t.u. per minute with an emissivity factor of 110. "For'dull stainlessisteel this factor is about :65, which will transfer about'23'00 B.t.u. per minute. "In addition, there is a convection transfer, which is about 200 B.t.u. per minute. The total is about 2500 B.t.u. per minute, `and.approximato'ely .the lheat transfer requirement for obtaining Athe desired quench.

It is sometimes desirable yto quench ythe kcracked gas further than indicated above. This may bedone by making the quenchers 50 and 51 thickerV andtheuetubes 81 longer, or by using a larger numberY ofisrnaller. ue tubes, to provide more quenching surface.

It is also desirable in .some casessml supplyfsteam to theV spaces 22 and 23'during the make'steps to provide an `additional quench. .To accomplish this', during 'a LH -make stepV as shownin'Fig. 2, the .fuel valves43. and 44 are closed and thesteam valve 44a.is:opened to supply steam at the .correctfpressure' to themanifold 56, the pipes V54, .and the nozzles 71'.toinject steam into v'thexspace 23 -countercurrent to Vtheflow' o'fvcrackedvgas therethrough.

Thus, the nozzles 71 .may 'serve the doublepurpose of supplying. fuell during vthe heat steps. and'steam for quench- Since the Vconstruct-ion and arrangement of the nozzles 71 are'designed for conditions required .for proper fuel.supp1y,the.steam pressure .must abe adiusted .torprovide .:-a 'proper supplyo'f .steam Ythere'through'for quenching. If it is desired yto .obtanjia A.steam'quench of the cracked gas at 200 C., saturated steam at an initial temperature of about 150 C. is supplied through the quencher 51, and the cracked gasmix- `ture will be reduced from 1075 C. to 875 C. Ifthe ltotal volume of the-cracked gas mixture is 275 s.'c.f.m. it vwillrrequire about 2550 B.t.u. for such quenching. The temperatureof the quenching steam will be increased from 150`1C.\.to..about.875 C., which requires a'ow of quenching steam of about 75 .s.c.f.m., or about 11.5 1s.c`.f.m. per nozzle 71,. and toaccomplish this .will require la pressure of about 18 p.s.i.g. on the supplyof quenching steam. Since the quenching steam is discharged into the spaces 22.and 23 during themakesteps and countercurrent to the flow of cracked gas therein it causes. a `high degree of turbulence inthe spaces, which quenchesthe cracked .gas quickly asfit leaves the center'rnass 25. This isanother advantage and object of theinvention. The partially. quenched cracked gas then flows through the quencher v50 or 51 where the temperature is further reiduced.l as explained above. By these two quenches Vthe temperature of vthe .cracked gas can readily be reduced at `least. 400 C. if desired.

.There are two important limitations on the operating :temperatures-of ythe quenchers 50 and 51 to insure proper operation of the furnace. First, if the fuel gas passing through Lthe. fuel pipes .54 and the orifices 77 Dis heated -rnuch .beyond 600C., some cracking of the fuel gas occurs zto produce undesirable tars which tend to plug the orifices.V Therefore, ythe temperatures within the `quenchers'should not. exceed 600 C. Secondly, if the -temperature in the vquenchers falls below the dew point .of .tarsrin` the cracked gas, such ,tars will Adeposit on the --quenchers to reduce the heat transfer characteristics .thereof and .to tend to plug the` Hue tubes 81. With Acracked gases normally formed in my'furnace, the dew point of such tars is normally somewhat below-300"v C. fandtoprevent Ythe deposit of vsuch tars this is theminimumpermissible temperature of the quenchers. Normally -.the furnace should .be operated on heating steps vonly until the temperature of the quenchers 50 and 51 is raised above 300 C. before cracking is started, and Vthereafter the temperature of the quenchers should be ymaintained .below 600 C.

.An alternative .form .of .nozzle element 71a isgshown :in; Fig.` 14 in `which .the only difference from the .nozzle .element 71a is in theplug 75a. In this form, the'outer end of the plug a is closed by a wall 7517 having a plu rality of orifices 75e therein which are directed radially andfoutwardly, 'and the orices 77a which admit gas or steam tothe interiorof the plug are enlarged. With this construction, fuel ejected from the orifices 75C crosses `the path of air owing through the flue tubes 81 and provides an improved mixing of the fuel and air during-a heat step to give more uniform combustion.

From the foregoing description it will be understood that the cross-sectional area of such a furnace may be scaledup or down as desired to provide any desired fur- -nace capacity within a wide range, providing furnace capacities greatly in excess of those attainable with .conventionalregenerative furnaces. This is an important object of the invention.

The transverse members 50 and 51 also serve a'further A,purpose in acting as baffles tending to confine the pyrolysis 0f the in-gas during each make step to the relatively short Zone therebetween, 'which materially increases the yield of the desired hydrocarbon.

The air passing through the member 51 is at a'higher `temperature than the member 51 due to having absorbed heat from the mass 17. Some drop in temperature, therefore, occurs at this point. However, the heat exchanger "'64 takes heat from both transverse members 50 and 51 and the blower 66 supplies air to the pipe 27 through the .valve.32,.which. adds heat to the air enteringthe mass'17 1in :amount approximately double that .removed from :ithe

airl by the' member 51. Also, sincethese furnaces are normally operated in pairs, all of the heat removed by the members 50 and 51 of the furnace which is on the cracking cycle is added to the air supplied to the furnace on the heat cycle. Therefore, the net result is that the heat added to the air before it enters the mass 17 is four times the heat removed by the member 51 less, of course, the normal loss in heat transfer. Conversely, during the right-hand heat step, air passing through the transverse member 50 is cooled but, before entering the mass 15, it is heated to the extent of four times this heat removal by means of the heat exchanger 64, which transfers heat to the air supplied to the valve 31 and the pipe 26.

While I have described a preferred embodiment of this invention, it will be apparent to those skilled in the art that its novel features may be applied in other equivalent forms, and I do not desire to be limited to such specific embodiment disclosed but desire to be afforded the full scope of the following claims.

I claim as my invention:

1. In a regenerative furnace for the pyrolysis of hydrocarbons, the combination of: a first regenerative mass; a second regenerative mass axially aligned with and 1ongitudinally spaced from said first mass to provide a first combustion space therebetween; a third regenerative mass axially aligned with said first and second masses and longitudinally spaced from said second mass to provide a second combustion space therebetween; a first fuel injection means extending into said first combustion space and having a plurality of nozzles in said space all directed axially of the furnace and only towards said second mass; and a second fuel injection means extending into said second combustion space and having a plurality of nozzles in said space and all directed axially of the furnace and only towards said second mass.

2. In a regenerative furnace for the pyrolysis of hydrocarbons, the combination of: first and second regenerative masses axially aligned and spaced apart to provide a combustion space, each of said masses having a plurality of longitudinal gas channels therethrough communicating with said combustion space; means for injecting fuel into said combustion space, including a plurality of nozzles; and transverse bale means in said combustion space and completely extending thereacross, said baffle means having a plurality of openings therethrough to provide communication between the channels in said first mass with the channels in said second mass, the total cross-sectional area of said openings being at least as great as the smallest total cross-sectional area of the channels in either of said masses, said openings being independent of and spaced from said nozzles.

3. In a regenerative furnace for the pyrolysis of hydrocarbons, the combination of: a first regenerative mass; a second regenerative mass spaced from said first mass to provide a first combustion space therebetween; a third regenerative mass spaced from said second mass to provide a second combustion space therebetween, each of said masses having a plurality of longitudinal gas channels therethrough communicating with the adjacent space or spaces; means for injecting fuel into each of said combustion spaces, including a plurality of nozzles; and transverse bafiie means in each of said combustion spaces and extending completely thereacross, each of said baffle means having a plurality of openings therethrough to provide communication between the channels of the masses on each side of such baie means, the total cross-sectional area of said openings in each of said baiiie means being at least as great as the smallest total cross-sectional area of the channels in any of said masses, said openings being independent of and spaced from saidv nozzles.

4. In a regenerative furnace for the pyrolysis of hydrocarbons, the combination of: first and second regenerative through said space, and through the other of said masses :through ciniunicating with said space; conveying means for conveying a cooling fluid through a predetermined confined path from the exterior of the furnace into and through said space and out -of the furnace, said path being separated from gases in said space; and a heat exchanger external to the furnace and associated with sai-d conveying means for recovering at least a part of any heat gained by said cooling fluid during its passage through said space and for cooling .said cooling fluid.

5. In a regenerative furnace for the pyrolysis of hydrocarbons, the combination of: first and second regenerative masses spaced apart to provide a combustion space therebetween, each of said masses having longitudinal channels therethrough communicating with said space; fuel means for supplying fuel to said space; air means for supplying air to the end of one of said masses remote from said space; conveying means for conveying a cooling fiuid through a predetermined confined and tortuous path from the exterior of the furnace into and through said space and out of the furnace, said path being separated from said space; and heat exchanger means external to the furnace and associated with said conveying means and said air means for imparting some of the heat of said cooling fluid in said conveying means to air to be supplied to the furnace by said air means.

6. In a regenerative furnace for the pyrolysis yof hydrocarbons, the combination of: first and second regenerative masses spaced apart to provide a space therebetween, each of said masses having a plurality of longitudinal gas channels therethrough communicating with said space and adapted to convey gases to or from -said space; a closed container extending into said space from thee'xterior of thefurnace so as to completely fill the cross-sectional area of said space but having a thickness substantially less than the length of said space between said masses; a plurality of fuel pipes within said container; a plurality of nozzles associated with each ofV said fuel pipes and extending from said container towards one of said masses; means for supplying fuel to said fuel pipes so as to be ejected through said nozzles into said space; a plurality of flues associated with said container and passing therethrough to provide communication between said space on one side of said container and said space on the other side of said container; bafe means in said containerA for directing a flow of fluid therethrough around said nozzles and said flues; and means for supplying fluid to and removing it from the interior of said container.

7. A method of operating a regenerative furnace hav` ing two spaced regenerative masses and a space therebetween, including the steps of: heating one of said masses to a temperature adapted to crack a suitable hydrocarbon in an in-gas; conveying such an in-gas through said one of said masses, through said space, and through the other of said masses so as to crack a substantial portion of said in-gas in said one of said masses; conveying a cooling fluid in a predetermined confined and tortuous path through said space during the passage of the cracked gas through said space; and maintaining the temperature of said cooling fluid substantially below the maximum temperature of the cracked gas during the passage of said cracked gas through said space so as to cool said cracked gas substantially.

v 8. Amethod of operating aA regenerative furnace having two spaced regenerative masses and a space therebetween, including the steps of: heating one of said masses` to a` temperaturel adapted to crack a suitable hydrocarbon in an in-gas and in excess of 800 C.; conveying such an in-gas through said vone of said masses,

' so as-to crack a substantial portion of said in-gas yin of said masses having longitudinal gas channels'theresaid one of said masses, the cracked gas passing from `said one of said` masses into said space at'a temperature in excess of 800 C.; conveying a cooling duid in a pre# 1'1 ldeterminedconned' and tortuousfgp ath` throughs aid*v space iduringvthe passage of the cracked gasthrough saidspace; land-maintaining the temperature of said cooling fluidv substantially belowthe maximum temperature ofthe cracked ,gas :during thepassage of said cracked gas throughV -said space so as to cool said cracked gasat least 100 C.

l9. Acyclic method of-operating a regenerative furnace having rstysecondrand third regenerative masses spaced lapart to form a iirstspacebetween .the first and second `masses andfa second space between the `second and thirdV masses,iirst quenching and fuel'injection means in the 'frst 'space and second quenching and fuel injection means in-'the second space, including the stepsof: a` i'irst heating 1step consisting Yof conveying-'air through ythe first -mass iand into the first space, injecting a fuel gas .through the v`"iirst injection means into the .rst space, combusting the uel -gas in the r'irst space-and. passing the products of v"coml'lustion through the second mass, the second space and the third mass to heat the'second and third'masses, the

"fuel gasbeing adapted to beat least partially cracked by fexposure toa predetermined elevated temperature, and I'maintaining the temperature of vthe'irstlfuel injection :means at a temperature below vsaid predetermined elevated temperature; a first cracking step consisting of conveying an in-gas through the third mass and'into the 'second space, through the second space and through the second mass, first space and tirstmass .to crack vthe in- Y gasinithe third and second .masses to produce a cracked gas containing a desired hydrocarbon and tarl-ike materialswand to quench the cracked gas in-the rst spaceby fthe iirst 'quenching means and maintainin-g -the -rst quenching means at'atemperature above the dewV point 'of said tarlike materials; a secondl heating-v step consisting .of conveying air through the third mass and into-the v*second space, injecting such a fuel gas through the second injection means into the. second space, combusting the .fuel gas in the second space and passingfthevproducts fof `combustion through the second mass,'the first space fand the rst mass to heat the second Iand rst masses,

:and `maintaining the temperature of the second fuel injection means at a temperature below said predetermined :elevated temperature; a second cracking step consisting of Vconveying such an in-gas through the tirst mass and into 'the .rst space, throughthe 'first space Vand through the second mass, second. space, and third mass to crack the' `xn-igas in the'rstand secondmasses to produce such-a :cracked gasandto quench the same in the second space by the second quenching means, and maintaining the sec- 'ond'rquenching means at a temperaturel above the-.dew

v:point of said ltat-like Vmaterials in the-cracked gas; and repeating said steps.

.'10. :In a regenerative furnace forthe pyrolysis of hyv.drocanbons, the combination of:

"first and second regenerative masses spaced apart to provideaspace therebetween, each of said masses having a plurality of longitudinal gas channels therethrough 'communicating with said space-and adapted to convey gasesrto or from said space;

v:a :transverse member in said spaceand completely lling the'cross-sectional area of said space buthaving .a thickness substantially less than the length of said space so that the member is spaced from each of saidregenera- -fdrocarbens fthe'. combination: of;

erst fand.; second :regenerative masses.- vspacedapartf .to

v-provide. aspace therebetween, each of said masses hav- .iing'apluralityoflongitudinalgas channels therethrough :communicating with said space and adapted torconvey gases `to :or from said space;

:a transverse l,member in said :space and Vcompletely lling the cross-sectional area of said space but having :a thickness substantially less than the length of said space `so that the member is spaced from each of said regenera- -tive masses;

a plurality of uninterrupted :ues throughrsaid transverser-member, each of saidfiues providing communication 4through said transverse member from one side to the other side thereof, said uesbeingevenly distributed -throughout the cross sectional area of the transverse member;

Va plurality of nozzles associatedwithisaid transverse member, said nozzles being evenly distributedl throughout the cross-sectional area ofsaid member `andindependent of said ues, said nozzles beingadapted to ldirect auid'ilow'from the interior of said transverse member into s-aidspaceaon one sidey of-said member;

'means for supplying a uid flow `through .said trans verse member to said nozzlespand passage-means for conveying a cooling medium. through ythe interior of said transverse Ymember and adjacent to saidilues-an'd nozzles to cool said .transverse member and *said flues and nozzles.

ll2. In a regenerative furnace for the pyrolysis oi? vhydrocarbons, the combination lof:

rst `and second .regenerativeimasses spaced apartto providea space therebetween, -each of said Vmasses `having a plurality of longitudinaligas-channelstherethrough communicating with said vspacerand adapted to` convey gases to or from said space;

-a transverse .member in said space and "completely 'filling'. the cross-sectional area of saidspace but having va thickness substantially less .than kthe lengthoffsald vspace so that the member .is spaced fromeach of said regenerative masses;

a plurality of uninterrupted'iiues through said transverse member, each ofsaid ues providing communication through said transverse member from one side to the 'other Aiside? thereof, f said ytiues being :evenly V.distributed throughout 'the cross-sectional area of the transverse mem- Y ber;

passage means for Y conveying a cooling medium throughthe interior of said transverse memberfanda'djacent to. said vlues to cool said transverse'member'and said ues;

-supply means -for supplying gaseous material to the end `of said tirst regenerative mass remote fromsaid space', Aand .heatexchanger means externa1-to the. furnace, said passage means yand said supply means vpassinghthrough saidl heat exchanger means in-heatexchangeirelationship so thatrheat fromthecooling medium yin said passage means. is transferred to saidl supply means to heat gaseous material Ytherein and-tto cool said cooling medium.

:13.A method ooperating aregenerativefurnace hav- `ing two rspaced regenerative masses and a space-therevbetween,:including the steps of:

:heating one of said massesto a temperatureadapted to crack a suitable hydrocarbon in an in-gasandin; excess of;800 C.;

"conveying such V: an in-gas through `said one .of ,.-said .massen through said kspace,fand through the other of lsaid masses so asto crack a substantial-portionfof said in-gas insaid one ofl said .masses, the crackedgas passing from said vone of said massesrinto.saidrspacet'at a temperatureineXcess of 800 C.;

" *conveyingfal coolingliquidin :a `predetermined confined sand'l tortuous `path through said space vdur-,ing- .thepassage asamoa of the cracked gas through said space, said cooling liquid having a Iboiling point substantially above 260 C.; and

maintaining the temperature of said cooling liquid substantially below the maximum temperature of the cracked gas during the passage of the cracked gas through said space so as to cool said cracked gas at least 100 C., the temperature of the liquid being maintained above 260 C. and below the boiling point of the liquid.

References Cited in the fue of this patent UNITED STATES PATENTS Hasche Dec. 12, 1950 Hasche et al. Oct. 26, 1954 Eastman et a1. Feb. 8, 1955 Pichler Oct. 2, 1956 Krejci Feb. 12, 1957 Begley Mar. 12, 1957 

1. IN A REGENERATIVE FURNACE FOR THE PYROLYSIS OF HYDROCARBONS, THE COMBINATION OF: A FIRST REGENERATIVE MASS, A SECOND REGENERATIVE MASS AXIALLY ALIGNED WITH AND LONGITUDINALLY SPACED FROM SAID FIRST MASS TO PROVIDE A FIRST COMBUSTION SPACE THEREBETWEEN, A THIRD REGENERATIVE MASS AXIALLY ALIGNED WITH SAID FIRST AND SECOND MASSES AND LONGITUDINALLY SPACED FROM SAID SECOND MASS TO PROVIDE A SECOND COMBUSTION SAPCE THEREBETWEEN, A FIRST FUEL INJECTION MEANS EXTENDING INTO SAID FIRST COMBUSTION SPACE AND HAVIG A PLURALITY OF NOZZLES IN SAID SPACE ALL DIRECTED AXIALLY OF THE FURNACE AND ONLY TOWARDS SAID SECOND MASS, AND A SECOND FUEL INJECTION MEANS EXTENDING INTO SAID SECOND COMBUSTION SPACE AND HAVING A PLURALITY OF NOZZLES IN SAID SPACE AND ALL DIRECTED AXIALLY OF THE FURNACE AND ONLY TOWARDS SAID SECOND MASS.
 7. A METHOD OF OPERATING A REGENERATIVE FURNACE HAVING TWO SPACED REGENERATIVE MASSES AND A SPACE THEREBETWEEN, INCLUDING THE STEPS OF: HEATING ONE OF SAID MASSES TO A TEMPERATURE ADAPTED TO CRACK A SUITABLE HYDROCARBON IN AN IN-GAS, CONVEYING SUCH AN IN-GAS THROUGH SAID ONE OF SAID MASSES, THROUGH SAID SPACE, AND THROUGH THE OTHER OF SAID MASSES SO AS TO CRACK A SUBSTANTIAL PORTION OF SAID IN-GAS IN SAID ONE OF SAID MASSES, CONVEYING A COOLING FLUID IN A PREDETERMINED CONFINED AND TORTUOUS PATH THROUGH SAID SPACE DURING THE PASSAGE OF THE CRACKED GAS THROUGH SAID SPACE, AND MAINTAINING THE TEMPERATURE OF SAID COOLING FLUID SUBSTANTIALLY BELOW THE MAXIMUM TEMPERATURE OF THE CRACKED GAS DURING THE PASSAGE OF SAID CRACKED GAS THROUGH SAID SPACE SO AS TO COOL SAID CRACKED GAS SUBSTANTIALLY. 